The present invention relates to coupling agents for covalent conjugation of proteins for use in diagnostic assays.
It is well established that a protein such as an enzyme can be conjugated via a linker group to another protein such as an antibody to form a conjugate which can be used in enzyme immunoassays (EIAs).
In the past, conjugates have been formed using heterobifunctional reagents which are quite short in comparison with the protein molecules being conjugated. It is believed that by restricting the conformational freedom of a protein, the function of the protein (e.g., initial rate, turnover number, and Km for an enzyme, or K.sub.aff for an antibody) can be adversely affected, thereby rendering the individual components of an enzyme-antibody conjugate less active than their unconjugated counterparts. This has been a problem which has limited the bioactivity of enzyme-antibody conjugates and their application to immunoassays.